A dot-matrix liquid crystal display is formed by confining a thin layer of liquid crystal material between a transparent front plate having a front electrode, and a back plate having a matrix of back electrodes corresponding to dots or pixels. Individual dots are optically responsive to voltages applied across the liquid crystal material sandwiched between the front electrode and corresponding back electrodes. Alternating voltages are used to drive dot-matrix liquid crystal displays in order to avoid well known direct voltage drive problems such as electrolytic plating of the electrodes and electrochemical breakdown of the liquid crystal material.
Dot-matrix liquid crystal displays may be of the active-matrix or passive-matrix liquid crystal display types. When used as low power, flat panel substitutes for cathode-ray tubes, their drive circuitry commonly drive the dot-matrix liquid crystal displays from conventional cathode-ray tube (CRT) video, horizontal synchronization (HSYNC), and vertical synchronization (VSYNC) signals. When applying alternating voltages to both the front and back electrodes in such applications, contrast uniformity among the dots of the dot-matrix liquid crystal display may suffer for one or more display or frame refresh cycles following each alternation of the front electrode voltage. The problem is particularly bothersome in liquid crystal display (LCD) projection systems employing dot-matrix liquid crystal displays characterized by high dot densities in small display areas.